| Diagnosis: |
Stems up to 48 cm high, of dark brown color and polysiphonic over a great part of their length. Main stem slightly geniculate. Branching starting at basal part of colony, frequent, in one plane, and approximately alternate. Branches distinctly constricted at their origin, originating at an angle of ca 45°, curving and running more or less parallel to the original branch. Branches with irregularly arranged perisarc constrictions. Hydrothecae present all over the colony, although invisible in polysiphonic parts. Hydrothecae usually arranged in decussate verticils of three to six hydrothecae, forming 6 to12 longitudinal rows; however, decussate pairs of hydrothecae
may be present in youngest, distal branches. Hydrothecae sunken into the branches and stems for approximately half of their volume, adcauline wall adnate for almost full length. In lateral view hydrotheca cylindrical, slightly curved abcaudally. In frontal view maximum diameter at hydrothecal base and then slowly decreasing in diameter towards the aperture. Hydrothecal aperture either even and approximately circular, or uneven with a more or less distinct prolongation of the abcauline hydrothecal wall, making the aperture laterally depressed. Hydrothecal aperture either tilted downwards, forming an acute angle with the
longitudinal axis of stem, or tilted upwards, being more or less perpendicular to long axis of branches. Rim of hydrothecal aperture sometimes with a few shallow renovations. Diaphragm mushroom-shaped. |